Regex Test API

POST https://api.findutils.com/api/tools/regex-test/execute

Test a JavaScript regular expression against input text. Returns every match (up to 1000) with its index, its numbered capture groups (captures: $1, $2, …, null for a group that did not take part) and its named groups. With replace, also returns the text after String.prototype.replace, which understands $1, $<name>, $&, $` , $' and $$ and replaces every match only when the g flag is set. Input past 50,000 characters is cut and marked truncated. Patterns with nested quantifiers are refused.

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Request body

application/json

pattern

string required

Regex pattern (max 500 chars).
input

string required

Text to search.
flags

string optional

Regex flags (g/i/m/s/u/y). Defaults to "g". Default "g".
replace

string optional

Optional replacement string, e.g. "$2-$1" or "$<year>". When given, the result includes replaced.

Example arguments

Verified

{
  "pattern": "^[a-z]+$",
  "text": "hello"
}

curl -X POST https://api.findutils.com/api/tools/regex-test/execute \
  -H "Content-Type: application/json" \
  -d '{
    "pattern": "^[a-z]+$",
    "text": "hello"
  }'

const response = await fetch('https://api.findutils.com/api/tools/regex-test/execute', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({"pattern":"^[a-z]+$","text":"hello"}),
});
const data = await response.json();

import requests

response = requests.post(
    "https://api.findutils.com/api/tools/regex-test/execute",
    json={"pattern":"^[a-z]+$","text":"hello"},
)
data = response.json()

$ch = curl_init('https://api.findutils.com/api/tools/regex-test/execute');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_HTTPHEADER => ['Content-Type: application/json'],
    CURLOPT_POSTFIELDS => '{"pattern":"^[a-z]+$","text":"hello"}',
    CURLOPT_RETURNTRANSFER => true,
]);
$data = json_decode(curl_exec($ch), true);

Also an MCP tool

Call regex_test from Claude, Cursor or any MCP client. Same arguments, same output.

https://mcp.findutils.com

MCP reference

Rate limit: 60 a minute, per IP
Auth: None
REST id: regex-test
MCP name: regex_test
Category: Developer
Machine-readable: openapi.json · markdown.md

Request body

Example arguments

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